1. Field of the Invention
The present invention relates generally to a vacuum processing chamber. More specifically, the present invention relates to a method and apparatus for in situ cleaning of a vacuum chamber surface and a surface of a component in the chamber.
2. Background of the Related Art
During fabrication of integrated circuits and flat panel displays, substrates are typically held by a substrate chuck which uses either a vacuum, mechanical, electrical or magnetic means to hold a substrate in place. These chucks are typically constructed of either ceramic or aluminum. Recently, electrostatic ceramic chucks have become widely used, and one exemplary electrostatic ceramic chuck is the MCA.TM. electrostatic ceramic chuck available from Applied Materials, Inc., of Santa Clara, Calif. Typically, electrostatic chucks are used in semiconductor processing chambers and systems such as the Endura.TM. system available from Applied Materials, Inc., Santa Clara, Calif. In the case of ceramic electrostatic chucks, it is critical to maintain a good dielectric layer between the chucking electrode and the substrate so that an appropriate electrostatic charge can be established on the chuck to hold the substrate in place. However, as a chuck holds a substrate during processing or is covered during cleaning, material from the process, as well as dirt, metal dust, chemicals, and other debris, can adhere to or react with the chuck, especially at high temperatures. These contaminants hinder the ability of the chuck to establish a charge separation required to properly hold the substrate on the chuck. The formation of a conducting layer on the surface provides an electrical path for the charge, resulting in leakage of the charge to the substrate and a loss of the chuck's ability to hold a substrate. To restore the chuck's ability to hold a substrate, the chuck must be periodically cleaned.
One method of cleaning a ceramic chuck involves filling the chamber with argon and applying a bias to the chuck that creates a plasma bombardment of the chuck to effect sputter cleaning of the surface. However, each application of argon plasma bombardment cleaning typically removes about 50 angstroms of material from the chuck, and as repeated cleaning erodes the outer surface of the chuck, the chuck becomes un-useable and needs to be replaced.
Another method of cleaning a ceramic chuck is a wet cleaning process which requires the system to be first vented to atmospheric pressure, then opened, cleaned, and subsequently returned to vacuum. Wet cleaning procedures typically require a washing step using an acid, followed by a light base cleaning step. Wet cleaning also typically requires a subsequent drying step which takes up tremendous valuable time and drastically reduces throughput.
UV radiation/ozone processes have been applied to the cleaning and stripping of contaminants from silicon substrates. One method, as disclosed in U.S. Pat. No. 5,480,492, cleans a surface of a silicon substrate by heating the contaminants thereon to a temperature greater than 750.degree. C. and simultaneously applying ultraviolet rays and oxygen molecules to the surface. However, this method is unsuitable for chamber cleaning because it requires a high temperature, produced by heaters such as lasers, that can cause damage to some surfaces.
U.S. Pat. No. 5,531,857 discloses an apparatus which uses a robot having gas passages and radiation passages therein to deliver UV radiation and gas to clean a surface within a chamber. However, this device does not meet the needs of modem vacuum semiconductor substrate processing because it is bulky, operates slowly, and is itself subject to the same contamination that threatens the chuck and other interior surfaces of the vacuum processing chamber because it is disposed within the processing chamber.
Therefore, there exists a need for an in situ vacuum processing chamber cleaning device and a process which operates quickly and reduces the process downtime for chamber cleaning. Preferably, the cleaning device occupies minimal operating space and is shielded from vacuum chamber processing operations.